Pre-populate audit tables

[jean-gui]

I think it would be nice if we had a way to pre-populate audit tables with the current content of the main tables. This would be useful for existing projects which would enable audit while there's already some data. That would allow us to keep a log of this original data even if it hasn't changed and seems more logical than having change events logged for entities that don't have a creation event recorded.

Additionally, this could help #98 for reverting deleted entities that existed before setting up this bundle.